Big Clive's "Trashy" meter, unboxed ( Duratool D03047 multimeter )

[robert.rozee]

This meter is CAT I 500V rated. I think that's a correct rating

i see that Fungus lives in country "00". it is a wonderful land, where if you just print "Cat I" onto a product, you are absolved from any and all responsibility. if someone burns off their hand, you are not responsible. if an explosion kills two people - the person holding the multimeter and a fireman standing next to him - then no worries, the "Cat I" label is completely and absolutely 100% flame and explosion proof, at least for the person who prints it onto the product. it also protects against legal liability and... most importantly, moral responsibility.

i feel that we should all move to country "00". it is a great place from which to offer our opinions.


cheers,
rob   :-)

[joeqsmith]

Agree, CAT I like most of us work with, the concern I have with the meters is if they survive.  I have no problem connecting any meter to the low energy sources I typically encounter.  Of course, normally I don't use them outside of their maximum ratings.   Still, shit happens and I have damaged my fair share of meters.  Which is why I ran these tests to get a feel for how robust the various brands are.   These tests have been conducted at low energy levels as I have never been concerned with safety.

All of the meters shown held up beyond their maximum ranges. 

This could maybe have been part of your robustness testing - how high will it go on the voltage range before it freaks out?

I don't normally connect a meter to a steady state source that is outside of it's rated limit.   Even at low currents the meter can be damaged.  I suspect there more than one fool watched one of my videos and saw me apply several kV to the same meter they owned and thought, hey, Joe shows my meter passed at 8kV so it should be fine to measure my 2kV MOT.       I've received dumb comments accusing me of connecting them directly to a capacitor bank or a DC source.   The worse are when they equate what I show to some sort of safety test.   

The most recent was a youtuber who claimed to work in education where they are involved with a EE program.   It's rare I will take the time to hunt someone down but in this case I made an exception.  Sure enough, they did not embellish their statements.   As fast as they pulled their comments after posting a link on this site, I assume they are a member.     

As far as the testing, I have seen what I was looking for.   Even with these low energy transients, chemical exposures and mechanical wear test, there is certainly a difference between brands.

[switchabl]

The "CAT I" marking is IMHO somewhat confusing and doesn't necessarily mean much in terms of overvoltage/transient protection.

The long story: there is the concept of "overvoltage categories" (defined for example in IEC 60664-1) which are essentially a classification that helps you to figure out necessary clearances, creepages etc. depending on overvoltages/transients that would be expected to occur in a circuit.

Those are related to, but not the same as, "measurement categories" which are supposed to tell the user of a measurement instrument whether it is safe to use it on a particular mains-connected circuit ("CAT ratings"). In particular, "overvoltage category I" is actually defined in terms of concrete impulse withstand voltages (e.g. 1.5 kV for a 300V supply mentioned above) while CAT I is not. IEC 61010-1 used to give concrete values for CAT II and higher and acknowledged that CAT I (not directly mains-connected) could cover a lot of different scenarios and the need for overvoltage protection would need to be determined (and documented) depending on the application.

Nowadays, the definition of the measurement categories has been moved to IEC 61010-2-030 and -033 and there is now only CAT II, III and IV as well as "equipment without a rated measurement category" (used to be CAT I). I suspect that the designation CAT I was removed because it was found to be confusing/inconsistent.

[IanB]

I'm curious--how many people here have actually plugged something into the mains that did not survive and which exploded as a result? My impression is that although the bang and the flash can be quite exciting, the main danger is likely to be flying shrapnel hitting your eyes, and therefore the most useful item of PPE would be safety glasses. I don't recall much mention of that in this thread, but if we were to offer useful safety advice to readers then I think the use of eye protection would be at the top of the list.

[joeqsmith]

I'm curious--how many people here have actually plugged something into the mains that did not survive and which exploded as a result?

 

Are you actually expecting the spirit of Billy Bob Ray to channel through one of the members here? 

[joeqsmith]

...
Nowadays, the definition of the measurement categories has been moved to IEC 61010-2-030 and -033 and there is now only CAT II, III and IV as well as "equipment without a rated measurement category" (used to be CAT I). I suspect that the designation CAT I was removed because it was found to be confusing/inconsistent.

I don't believe that's something new.  Even in EVS-EN 61010-2-033:2012 it was replaced with

O: Other circuits that are not directly connected to MAINS

, but I continue to see papers published that refer to CAT I. 

Fluke's application note:

ABCs of multimeter safety Multimeter safety and you

for example states:

CAT I Electronic • Protected electronic equipment
• Equipment connected to (source) circuits in which measures
are taken to limit transient overvoltages to an appropriately
low level
• Any high-voltage, low-energy source derived from a highwinding
resistance transformer, such as the high-voltage
section of a copier

With different countries all having their own twist on these standards (I assume to leverage for import export) the may not use the same definitions.   

If I were repairing toasters, I wouldn't be too concerned.   Even in the previous post, the fact they were mentioning  plugging into mains tells me something. 

[Fungus]

My impression is that although the bang and the flash can be quite exciting, the main danger is likely to be flying shrapnel hitting your eyes, and therefore the most useful item of PPE would be safety glasses.

The bang and flash could easily make you fall off a ladder. Or make you step backwards and put your foot in the bucket.

I don't recall much mention of that in this thread

You never will. The nannies assume that simply owning a yellow meter is sufficient protection. No gumboots needed.

I continue to see papers published that refer to CAT I. 

It's a useful designation. The "other" category still needs a name.

Roman numerals don't have zeros so maybe they could have renamed it "CAT X".

I suspect that the designation CAT I was removed because it was found to be confusing/inconsistent.

Me? I'd have picked CAT II as the "useless" category.

a) A single piece of wire can be CAT II at one end and CAT III at the other. It doesn't get much more "confusing/inconsistent" than that. 

b) Is there a real job where you only ever work at CAT II level and never at CAT III?

[switchabl]

...
Nowadays, the definition of the measurement categories has been moved to IEC 61010-2-030 and -033 and there is now only CAT II, III and IV as well as "equipment without a rated measurement category" (used to be CAT I). I suspect that the designation CAT I was removed because it was found to be confusing/inconsistent.

I don't believe that's something new.  Even in EVS-EN 61010-2-033:2012 it was replaced with

O: Other circuits that are not directly connected to MAINS

, but I continue to see papers published that refer to CAT I.

Yes, I just checked and DIN-EN 61010-1:2002 defines "measurement category I" (while 2010 does not). IEC 61010-2-033 didn't even exist back then, multimeters were covered by the general norm. I feel old now.

It's certainly true that it has stuck around. You even get new products with "CAT I" markings, even though AFAIK you were never really supposed to do that even back then (terminals with measurement category I are supposed to be labelled with the voltage rating, only the higher categories should have "CAT x" printed next to them).

What I hope people take away from this:
- CAT II, III, IV have very specific meanings in terms of overvoltage protection
- "CAT I" just means "not supposed to be connected directly to a mains circuit"; there may or may not be additional protection beyond the rated voltage, check the manual

If someone decides not to follow safety standards that is fine by me (as long as they do not endanger anyone else). I just think that this should be a conscious decision, not a result of ignorance or misinformation.

Me? I'd have picked CAT II as the "useless" category.

a) A single piece of wire can be CAT II at one end and CAT III at the other. It doesn't get much more "confusing/inconsistent" than that. 

b) Is there a real job where you only ever work at CAT II level and never at CAT III?

a) The difference between CAT II - IV circuits is basically all wiring (which adds impedance) and usually a fuse or circuit breaker somewhere between each level.

Anyway, the level of protection for CAT II is clearly defined and it means the same on any meter, whether you find it useful or not. The problem with CAT I was that is just says "could mean anything, read the manual".

b) Yes, anyone repairing or developing mains-powered electronics or appliances will usually need CAT II only (CAT III is for electricians).

[David Aurora]

You keep banging on about how these things work just fine at high voltages, then when you get called out you backtrack and claim you never said they were suitable for it.

Rubbish.

I said they were suitable for high voltage, and I stand by that. Pictures have been posted of a worse meter than this measuring 1100V in somebody's hand.

(I notice you don't go after joe...)

I also said they weren't suitable for high energy. If you can't understand the difference between the two then you're in no position to lecture anybody on safety.

This meter is CAT I 500V rated. I think that's a correct rating and said so in the very first post, anything else is just your imagination.

End of.

Right, because Joe clearly knows what he's talking about and also clearly knows the difference between safety based on knowledge and safety based on wilful ignorance.

Again, you're playing word games with voltage/energy as if there's no relation. A high voltage/low energy circuit can become a lethally high energy circuit pretty damn quickly under all sorts of fault or user error conditions. A correctly set meter being tested under controlled conditions with a sample size you can count on one hand is not an endorsement of a meter being suitable for use at high voltage.

Do what you want in your own time, but if you're gonna carry on on the internet about a poorly constructed hobbyist meter being suitable for high voltages be prepared for disagreement.

[joeqsmith]

I feel old now.

You and me both! 

What I hope people take away from this:
- CAT II, III, IV have very specific meanings in terms of overvoltage protection

As a general observation, meters that have been certified to the 61326 EMC standards do well against my tests.  The protection is a dice roll as what it even means.  Protect the meter, protect the operator, both...   Manufactures don't agree.   I was interested in finding meters that would not be damaged when subjected to a few basic transients.  It doesn't really fit with the IEC standards and why I rolled my own generator.   I wanted something like the 6100-4-5 surge but limited.  So I dropped the combo,  followed the open circuit voltage waveforms, ignored the short circuit current and limited it to about 20J.   Depending on the generator, I used a 50 or 100us FWHH and stayed with a 2 ohms source across the board.   

We did have a member how stepped up and ran a new Fluke 101 on a real combo generator after I tested that first one.  Crazy how robust these things are.  That was Fungus's contribution as I would have never purchased another Fluke otherwise as I was still pissed at them a few decades later for designing such a weak meter (8000A).      

[David Aurora]

I feel old now.

You and me both! 

What I hope people take away from this:
- CAT II, III, IV have very specific meanings in terms of overvoltage protection

As a general observation, meters that have been certified to the 61326 EMC standards do well against my tests.  The protection is a dice roll as what it even means.  Protect the meter, protect the operator, both...   Manufactures don't agree.   I was interested in finding meters that would not be damaged when subjected to a few basic transients.  It doesn't really fit with the IEC standards and why I rolled my own generator.   I wanted something like the 6100-4-5 surge but limited.  So I dropped the combo,  followed the open circuit voltage waveforms, ignored the short circuit current and limited it to about 20J.   Depending on the generator, I used a 50 or 100us FWHH and stayed with a 2 ohms source across the board.   

We did have a member how stepped up and ran a new Fluke 101 on a real combo generator after I tested that first one.  Crazy how robust these things are.  That was Fungus's contribution as I would have never purchased another Fluke otherwise as I was still pissed at them a few decades later for designing such a weak meter (8000A).   

Have you got any plans to torture test any bench meters? Unless I missed it I haven't seen any so far from you. I'd be really curious to see what you find

[Fungus]

b) Yes, anyone repairing or developing mains-powered electronics or appliances will usually need CAT II only (CAT III is for electricians).

OK, let's say I'm working on a PC power supplies in a large office building. How can I know for sure if the mains on my workbench is CAT II or CAT III? Am I supposed to trace the wires in the walls back to the distribution panel and measure how long they are before deciding what meter to use? That's the only way to follow the standard.

Let's suppose it's a company with a few different rooms with workbenches. Will all those rooms have the same CAT rating?

Should a professional or a company like that even make the effort to source/purchase CAT II meters? What would be the advantage? What brand/model would you advise them to buy?

[IanB]

Have you got any plans to torture test any bench meters? Unless I missed it I haven't seen any so far from you. I'd be really curious to see what you find

Are bench meters supposed to be robust? In my mind I think of them as sensitive, delicate, precision instruments, things to be treated with care. Would you expect an expensive Mitutoyo micrometer to survive being chucked in a tool drawer?

[Someone]

b) Yes, anyone repairing or developing mains-powered electronics or appliances will usually need CAT II only (CAT III is for electricians).

OK, let's say I'm working on a PC power supplies in a large office building. How can I know for sure if the mains on my workbench is CAT II or CAT III? Am I supposed to trace the wires in the walls back to the distribution panel and measure how long they are before deciding what meter to use? That's the only way to follow the standard.

Let's suppose it's a company with a few different rooms with workbenches. Will all those rooms have the same CAT rating?

Should a professional or a company like that even make the effort to source/purchase CAT II meters? What would be the advantage? What brand/model would you advise them to buy?

Sounds identical to the grumbling in another recent low cost multimeter thread: https://www.eevblog.com/forum/testgear/aneng-sz20-25-000-count-1uv-10na-20a/
Is it plugged into a mains socket outlet, but lacks at least 1 form of isolation? You're in CAT II land.

Someone else has done the hard work and figured out the probability of seeing something outside of CAT II at a mains outlet is vanishingly improbable (assuming everything upstream of there is installed to your prevailing standards). Broad categories that encompass close to worst case conditions.

[EEVblog]

BTW, the DT830 meter was designed by Li Hong in 1984, the founder of Zotek, as per my recent video.

[Fungus]

Someone else has done the hard work and figured out the probability of seeing something outside of CAT II at a mains outlet is vanishingly improbable (assuming everything upstream of there is installed to your prevailing standards). Broad categories that encompass close to worst case conditions.

Yes, but:

a) You can't tell if it's a CAT II mains socket just by looking at it so what meter should you use?
b) Is there any point in buying a meter for mains work that's limited to CAT II? (eg. Is it much cheaper? What...?)

[robert.rozee]

a) You can't tell if it's a CAT II mains socket just by looking at it so what meter should you use?
b) Is there any point in buying a meter for mains work that's limited to CAT II? (eg. Is it much cheaper? What...?)

what on earth has this got to do with the discussion of a meter marked "Cat I"?!

the argument over the difference between "Cat II" and "Cat III" designation is a sideshow, please start a new thread about it.


cheers,
rob   :-)

[Fungus]

the argument over the difference between "Cat II" and "Cat III" is a sideshow, please start a new thread about it.

Not a bad idea.

[Someone]

Someone else has done the hard work and figured out the probability of seeing something outside of CAT II at a mains outlet is vanishingly improbable (assuming everything upstream of there is installed to your prevailing standards). Broad categories that encompass close to worst case conditions.

Yes, but:

a) You can't tell if it's a CAT II mains socket just by looking at it so what meter should you use?
b) Is there any point in buying a meter for mains work that's limited to CAT II? (eg. Is it much cheaper? What...?)

Every mains socket outlet is CAT III, things plugged into it are CAT II until they reach safety isolation at which point the electronics beyond there can become CAT I. Why is this so hard to understand?

[David Aurora]

Have you got any plans to torture test any bench meters? Unless I missed it I haven't seen any so far from you. I'd be really curious to see what you find

Are bench meters supposed to be robust? In my mind I think of them as sensitive, delicate, precision instruments, things to be treated with care. Would you expect an expensive Mitutoyo micrometer to survive being chucked in a tool drawer?

Are you talking about drop tests etc? I'm talking about surges/spikes/overload conditions/etc

[Fungus]

Edit: Discussion forked to Here: https://www.eevblog.com/forum/testgear/is-cat-ii-a-useful-rating/

You can't tell if it's a CAT II mains socket just by looking at it so what meter should you use?

Every mains socket outlet is CAT III

Fluke's notes say:
CAT III:
Appliance outlets with short connections to service entrance

CAT II:
Outlets at more than 10 meters (30 feet) from CAT III source.
Outlets at more than 20 meters (60 feet) from CAT IV source.

I think it's a good idea to assume that a socket is CAT III when dealing with it, so that rules out CAT II multimeters.

things plugged into it are CAT II

You're saying the difference between CAT III and CAT II is an extra 1m of cable?

[EEVblog]

b) Yes, anyone repairing or developing mains-powered electronics or appliances will usually need CAT II only (CAT III is for electricians).

OK, let's say I'm working on a PC power supplies in a large office building. How can I know for sure if the mains on my workbench is CAT II or CAT III? Am I supposed to trace the wires in the walls back to the distribution panel and measure how long they are before deciding what meter to use? That's the only way to follow the standard.

The fact that it's a standard mains outlet on bench pretty much puts it in the CAT II range.
Anything in a fuse box or plant room is CAT III at least, maybe CAT IV
Fluke have a handy guide.

Let's suppose it's a company with a few different rooms with workbenches. Will all those rooms have the same CAT rating?

Could technically depend on the distance, but a CAT III meter covers everything outside of a direct utility connection./

Should a professional or a company like that even make the effort to source/purchase CAT II meters? What would be the advantage? What brand/model would you advise them to buy?

If you work on anything mains, get CAT III minimum as a basic rule.

[Gyro]

It can be instructive to look at the breakers in the consumer unit / breaker panel in non-industrial settings. Standard IEC61009-1 breakers normally have a maximum breaking capacity of 6kA. It is the responsibility of the installing electricial to measure and ensure that the Zin is high enough and and the PSC low enough to fall within the limits of these breakers. In the case of my installation, the Zin is 0.12R, equating to a PSC of 2kA [Edit @240V], people often overestimate the prospective fault currents on their domestic installations, I've seen wild estimates in some threads. This does not cover short duration network induced voltage spikes of course, which are too fast to trip the breakers.

A competent electricial, in either industrial or consumer settings will ensure that they know such figures for the installation and ensure that their test equipment ratings exceed the prospective fault currents involved.

[EEVblog]

Have you got any plans to torture test any bench meters? Unless I missed it I haven't seen any so far from you. I'd be really curious to see what you find

Are bench meters supposed to be robust? In my mind I think of them as sensitive, delicate, precision instruments, things to be treated with care. Would you expect an expensive Mitutoyo micrometer to survive being chucked in a tool drawer?

I don't think I've ever seen a bench meter that is CAT III/IV rated, it's just not a thing.
e.g.

[Someone]

things plugged into it are CAT II

You're saying the difference between CAT III and CAT II is an extra 1m of cable?

FFS, the division between the categories has to be placed somewhere. Do you want to colour code your cabling and outlets to indicate their voltages and fault currents? and make everyone else in the world do the same? or perhaps introduce 43 new categories so you can define the difference between 1.2m and 1.8m supply leads?

There are 4 categories, each with really simple and easy to remember delineations, the almost worst case situation for each is what the measurement device needs to withstand. Keeps it to a manageable number of certifications/specifications and simplifies worldwide compliance.